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We control the motion of paramagnetic microparticles with average diameter of 100 µm inside microfluidic channels against and along time-varying flow rates. The drag force and the force due to time-varying flow rate are modeled as time-varying disturbance force. This force is estimated using a disturbance force observer and compensated using a magnetic-based closed-loop control system. The closed-loop control with disturbance compensation decreases the steady-state error by 81.4%, 70.2%, and 70.3% at flow rates of 6 ml.hr−1, 17 ml.hr−1, and 35 ml.hr−1, respectively. The proposed control system is essential to translate these paramagnetic microparticles and magnetic drug carriers into in vivo applications.

Introducción: En las últimas dos décadas, la implementación de técnicas quirúrgicas mínimamente invasivas ha colaborado en la reducción de las complicaciones intra y postoperatorias. Un amplio espectro de enfermedades del esófago, benignas o malignas, pueden ser tratadas por medio de estas técnicas. Objetivo: Se presenta nuestra experiencia en el tratamiento quirúrgico de la patología tumoral esofágica y se hace una revisión de las indicaciones y resultados publicados en la literatura internacional. Material y Método: Se trata de 85 pacientes operados desde 1993 a la fecha, 67 corresponden a cáncer esofágico, 14 casos operados por leiomomas o tumores estromales esofágicos y 4 pacientes con quistes de duplicación. Todos fueron sometidos a cirugía mini invasiva de acuerdo a técnicas descritas previamente. Se analizan y discuten los resultados a corto y largo plazo y se discuten los resultados a la luz de los datos de la literatura internacional. Resultados: En los pacientes sometidos a esofagectomía por cáncer, las complicaciones ocurrieron en 43% y la mortalidad actual es de un 2,9%. En pacientes operados por tumores estromales o quistes de duplicación no hubo complicaciones postoperatorias ni mortalidad. En las otras patologías hubo mínima morbilidad y no hubo mortalidad, resultados que son comparables a la literatura consultada. Conclusión: Las técnicas de cirugía mínimamente invasiva diseñadas para el abordaje de los diversos tipos de patologías que afectan al esófago, resultan por lo general, altamente factibles de realizar, con buenos resultados en cuanto a complicaciones y mortalidad postoperatoria.

Introducción: En este artículo se presenta la experiencia de nuestro grupo de trabajo de los resultados obtenidos en el tratamiento quirúrgico con técnicas mínimamente invasivas en patología esofágica benigna. Material y Método: Se analizan los resultados en pacientes sometidos a cirugía antirreflujo por enfermedad por reflujo gastroesofágico, esófago de Barrett, tratamiento de las hernias hiatales, acalasia esofágica y diver-tículos esofágicos. Resultados: Los resultados obtenidos por nuestro grupo son comparables a los que señala la literatura internacional, con mínima morbilidad y sin mortalidad. En pacientes con reflujo gastroesofágico, los resultados a largo plazo presentan una tasa de éxito en el 85% de los casos. En pacientes con hernia hiatal operados por vía laparoscópica las complicaciones son cercanas al 12% y la recurrencia es de un 12% en promedio, pero se eleva al 17% cuando no se usa malla. En Acalasia por otro lado, la tasa de recurrencia es menor a un 5%. Los pacientes operados por divertículos esofágicos no presentan recidiva. Conclusiones: Las técnicas de cirugía mínimamente invasiva diseñadas para el abordaje de los diversos tipos de patologías que afectan al esófago, resultan por lo general, altamente factibles de realizar por cuanto reproducen los resultados de la cirugía abierta pero con menor tasa de complicaciones.

Adults with Duchenne muscular dystrophy (DMD), due to their severe muscular weakness, cannot benefit from passive arm supports that only compensate for the weight of their arms. Active arm supports can potentially enable adults with DMD to perform activities of daily living, improving their independence, and increasing their participation in social activities. In this paper we present the A-Arm, an inconspicuous and simple planar active arm support for adults with DMD that can be controlled with force- or EMG-based interfaces. The A-Arm is intended to replace the arm rest of the wheelchair and assist during table top tasks such as computer, tablet, or smartphone use, writing and drawing, and the use of the wheelchair's joystick. In the force-based control interface we have implemented active compensation of the joint-stiffness forces using a measurement-based method to obtain an estimation of the voluntary forces of the user. A pilot evaluation with an adult with DMD (24 years-old, Brooke 5) has shown that the A-Arm was able to increase the functional workspace of the arm (from 100 cm2 to 190–200 cm2). We found that while force-based control was experienced by the participant as more fatiguing than EMG-based control, the movements with EMG-based control were less accurate. These preliminary results give promising perspectives for the use of simple active arm supports to increase the independence of people with DMD.

Adults with Duchenne muscular dystrophy (DMD) can benefit from active arm supports that augment the residual motion capabilities of their arms. While there is a considerable number of active exoskeletons commercially available for rehabilitation purposes, no active exoskeletons for supporting the arm function during the performance of activities of daily living (ADL) are available. In this paper, we present the Active A-gear, a wearable five degree-of freedom exoskeleton that has been specially developed to assist people with DMD for the performance of ADL. The Active A-Gear is built upon our previous design of the passive A-Gear, thus combining active and passive support. The Active A-Gear can be controlled using force-based (admittance) control. We report the results of the system verification, which included endpoint position bandwidth, workspace, weight, joint speed, endpoint force and joint backlash measurements. A pilot evaluation was carried out with one healthy subject (27 years-old) performing ADL. The results of the verification and evaluation tests indicate that with some modifications the Active A-Gear is a suitable platform to test the functional performance and feasibility of a wearable and active support for adults with DMD.

Wearable devices to assist abnormal gaits require controllers that interact with the user in an intuitive and unobtrusive manner. To design such a controller, we investigated a bio-inspired walking controller for orthoses and prostheses. We present (i) a Simulink neuromuscular control library derived from a computational model of reflexive neuromuscular control of human gait with a central pattern generator (CPG) extension, (ii) an ankle reflex controller for the Achilles exoskeleton derived from the library, and (iii) the mechanics and energetics of healthy subjects walking with an actuated ankle orthosis using the proposed controller. As this controller was designed to mimic human reflex patterns during locomotion, we hypothesize that walking with this controller would lead to lower energetic costs, compared to walking with the added mass of the device only, and allow for walking at different speeds without explicit control. Preliminary results suggest that the neuromuscular controller does not disturb walking dynamics in both slow and normal walking cases and can also reduce the net metabolic cost compared to transparent mode of the device. Reductions in tibialis anterior and soleus activity were observed, suggesting the controller could be suitable, in future work, for augmenting or replacing normal walking functions. We also investigated the impedance patterns generated by the neuromuscular controller. The validity of the equivalent variable impedance controller, particularly in stance phase, can facilitate serving subject-specific features by linking impedance measurement and neuromuscular controller.

Minimally invasive mitral valve (MV) repair surgery significantly reduces trauma compared to an open heart procedure, which enables fast recovery and treatment to high-risk patients. However, limited vision and dexterity of the instrument at the treatment location poses a challenge for minimally invasive surgery. Additionally, MV repair surgery performed without cardiopulmonary bypass often requires the surgeon to deal with beating heart motions. By autonomous stabilization of the instrument, a virtually-still treatment location could be provided. This allows the surgeon to perform surgery as if the heart was stopped. In this study, we present and evaluate a framework that assists the surgeon by stabilizing the instrument for the beating heart MV motions. Our work contributes a robotically-actuated delivery sheath (RADS), which is stabilized in a realistic and functional MV model embedded in a heart motion system. The heart motion system is mounted on a six degrees-of-freedom Stewart platform, which reproduces beating heart MV motions based on pre-operative patient data obtained from three-dimensional magnetic resonance and ultrasound images. Experimental results shows stabilization of the RADS in a beating heart MV model with a mean absolute tracking error of 1.31 mm. The presented framework for stabilization of the RADS in the beating heart could be applicable to a wide variety of existing and potential future cardiovascular interventions.

Robotically-Actuated catheters are being employed in endovascular interventions for their improved maneuverability and steering precision over conventional catheters. Fluoroscopy is commonly used to guide such medical devices during interventions. Motivated by the limitations and hazards associated with fluoroscopy, this study investigates the use of ultrasound images as a viable alternative for the real-Time visualization of a robotic catheter. In order to validate the proposed approach, an integrated system is developed which employs a two-dimensional ultrasound-based tracking algorithm to detect and track a magnetically-Actuated catheter. By using Euler-Bernoulli beam theory to describe the motion of the catheter and a closed-loop control, the magnetic field steers the robotic catheter in two-dimensional space. Experiments show that the model is able to describe the catheter deflections with a fitting error of R2 = 0.96. Closed-loop steering experiments show a maximum positioning error of 0.46 mm. Our study demonstrates the possibility to accurately steer a magnetic catheter using two-dimensional ultrasound images.

Robotic devices that are able to manipulate the fingers can support the study of robot-assisted motor learning. Currently no devices are available that provide a transparent haptic environment and provide a platform to study motor learning. To cut down on costs it is proposed to use remote control (RC) servos with admittance control. In this study five RC servos are tested to evaluate their controller and passive dynamic properties. Frequency and step response are evaluated and passive dynamics are estimated using a model fit. With a fitted frequency response, system stability is evaluated for different human impedances. The high speed servos have lowest passive inertia (2 ୷ 10−4 kgm2) and highest bandwidth (20 Hz). The communication protocol of RC servos causes a delay of more than 5 ms from change in setpoint to change in output. Stability analysis shows that the high speed servos have largest stability regions. Simulations show that reducing the virtual inertia and damping makes the system more susceptible to unstable behavior. At this moment however the passive dynamics of the setup are more transparent than the virtual inertia (1 · 10−3 kgm2) and damping that can be simulated with an admittance controller. A possible cause lies with the communication delay and high gearing present in RC servos.

Resumen La cirugía del cáncer de esófago ha sido y sigue siendo un desafío pese a los avances en técnica quirúrgica y cuidados peri operatorios y a pesar de que las complicaciones postoperatorias y la morbimortalidad sigue siendo alta, aún en centros con alto volumen de procedimientos y más aún en centros no dedicados a laatención de estos pacientes. En este artículo se revisarán algunos aspectos epidemiológicos, las herramientasdiagnósticas actuales, su etapificación, y las opciones terapéuticas de acuerdo al estadío, sea en etapas precoces o avanzadas, la localización y tipo de tumor, opciones de reconstrucción del tránsito digestivo en base alo reportado en la literatura internacional, la experiencia nacional y en base a nuestros propios resultados enel Departamento de Cirugía del Hospital Clínico de la Universidad de Chile. Abstract Esophageal cancer surgery is a challenge despite the advances in surgical techniques and perioperative care. It continues to have high rates of complications and mortality, even in large volume centers. This paperrevises the epidemiology, staging and therapeutic options for esophageal cancer, according to its stage andlocation. It also encompasses the digestive tract reconstruction options, according to our own experience andreports from abroad.

Resumen La cirugia del cancer de esofago ha sido y sigue siendo un desafio pese a los avances en tecnica quirurgica y cuidados peri operatorios y a pesar de que las complicaciones postoperatorias y la morbimortalidad sigue siendo alta, aun en centros con alto volumen de procedimientos y mas aun en centros no dedicados a laatencion de estos pacientes. En este articulo se revisaran algunos aspectos epidemiologicos, las herramientasdiagnosticas actuales, su etapificacion, y las opciones terapeuticas de acuerdo al estadio, sea en etapas precoces o avanzadas, la localizacion y tipo de tumor, opciones de reconstruccion del transito digestivo en base alo reportado en la literatura internacional, la experiencia nacional y en base a nuestros propios resultados enel Departamento de Cirugia del Hospital Clinico de la Universidad de Chile.

Background: Minimally invasive surgery has the advantage of a lower rate of complications and can be used for benign esophageal diseases. Aim: To report a single surgeon experience with laparoscopic surgery for benign esophageal diseases. Material and Methods: Prospective analysis of 421 patients (160 males) with benign esophageal disease, who were subjected to laparoscopic surgery by a single surgeon. Immediate mortality, surgical complications and long term results in terms of symptoms recurrence, were analyzed. Results: The underlying diagnoses of the operated patients were Barrett's esophagus or esophagitis in 257, hiatal hernia in 91, achalasia in 68 and esophageal diverticula in five. Surgery obtained successful results in 90% of patients with Barrett's esophagus. Among patients with hiatal hernia, there was a 12% rate of complications and a 30% recurrence, when a mesh was not used. Among patients with achalasia the recurrence rate was less than 5%. Conclusions: Laparoscopic surgery has a fair success rate in benign esophageal diseases, with a lower rate of complications.

Introducción: En las últimas dos décadas, la implementación de técnicas quirúrgicas mínimamente invasivas ha colaborado en la reducción de las complicaciones intra y postoperatorias. Un amplio espectro de enfermedades del esófago, benignas o malignas, pueden ser tratadas por medio de estas técnicas. Objetivo: Se presenta nuestra experiencia en el tratamiento quirúrgico de la patología tumoral esofágica y se hace una revisión de las indicaciones y resultados publicados en la literatura internacional. Material y Método: Se trata de 85 pacientes operados desde 1993 a la fecha, 67 corresponden a cáncer esofágico, 14 casos operados por leiomomas o tumores estromales esofágicos y 4 pacientes con quistes de duplicación. Todos fueron sometidos a cirugía mini invasiva de acuerdo a técnicas descritas previamente. Se analizan y discuten los resultados a corto y largo plazo y se discuten los resultados a la luz de los datos de la literatura internacional. Resultados: En los pacientes sometidos a esofagectomía por cáncer, las complicaciones ocurrieron en 43% y la mortalidad actual es de un 2,9%. En pacientes operados por tumores estromales o quistes de duplicación no hubo complicaciones postoperatorias ni mortalidad. En las otras patologías hubo mínima morbilidad y no hubo mortalidad, resultados que son comparables a la literatura consultada. Conclusión: Las técnicas de cirugía mínimamente invasiva diseñadas para el abordaje de los diversos tipos de patologías que afectan al esófago, resultan por lo general, altamente factibles de realizar, con buenos resultados en cuanto a complicaciones y mortalidad postoperatoria. Background: Minimally invasive surgery reduced the incidence of postoperative complications. Many benign or malignant esophageal diseases can be treated with this technique. Aim: To report our experience with the technique in the treatment of esophageal tumors. Material and Methods: Analysis of a cohort of 85 patients with esophageal tumors aged 28 to 82 years (59 males). Sixty seven had esophageal cancer, 14 had leiomyomas or esophageal stromal tumors and four had duplication cysts. All were subjected to minimally invasive surgery. Short and long term results were recorded. Results: Forty three percent of patients with cancer had complications and 2.9% died. No complications were recorded among patients with stromal tumors or duplication cysts. Conclusions: Minimally invasive surgery is a feasible and safe therapeutic approach for patients with esophageal tumors.

Introducción: En este artículo se presenta la experiencia de nuestro grupo de trabajo de los resultados obtenidos en el tratamiento quirúrgico con técnicas mínimamente invasivas en patología esofágica benigna. Material y Método: Se analizan los resultados en pacientes sometidos a cirugía antirreflujo por enfermedad por reflujo gastroesofágico, esófago de Barrett, tratamiento de las hernias hiatales, acalasia esofágica y diver-tículos esofágicos. Resultados: Los resultados obtenidos por nuestro grupo son comparables a los que señala la literatura internacional, con mínima morbilidad y sin mortalidad. En pacientes con reflujo gastroesofágico, los resultados a largo plazo presentan una tasa de éxito en el 85% de los casos. En pacientes con hernia hiatal operados por vía laparoscópica las complicaciones son cercanas al 12% y la recurrencia es de un 12% en promedio, pero se eleva al 17% cuando no se usa malla. En Acalasia por otro lado, la tasa de recurrencia es menor a un 5%. Los pacientes operados por divertículos esofágicos no presentan recidiva. Conclusiones: Las técnicas de cirugía mínimamente invasiva diseñadas para el abordaje de los diversos tipos de patologías que afectan al esófago, resultan por lo general, altamente factibles de realizar por cuanto reproducen los resultados de la cirugía abierta pero con menor tasa de complicaciones. Background: Minimally invasive surgical techniques are increasingly used for the treatment of benign esophageal diseases. Aim: To report the results of minimally invasive surgical techniques among patients with benign esophageal diseases. Material and Methods: Four hundred eighty three patients aged 37 to 81 years (184 males), were studied. Of these, 278 had a Barret esophagus, 125 had a hiatal hernia, 75 had achalasia and five had esophageal diverticula. All patients were studied using standard protocols, operated using minimally invasive techniques and followed, registering postoperative complications and recurrence of symptoms. Results: Among patients with esophageal reflux, 85% had successful results on the long term. Among patients with hiatal hernia and subjected to laparoscopic surgery, 12% had complications and 12% had recurrence of symptoms which increased to 17% if a mesh was not used. The recurrence rate among patients with achalasia is less than 5%. There was no recurrence among patients with esophageal diverticula. Conclusions: Minimally invasive surgery for esophageal diseases has good success rates, with a lower incidence of complications than open surgery.

Background: Minimally invasive surgery has the advantage of a lower rate of complications and can be used for benign esophageal diseases. Aim: To report a single surgeon experience with laparoscopic surgery for benign esophageal diseases. Material and Methods: Prospective analysis of 421 patients (160 males) with benign esophageal disease, who were subjected to laparoscopic surgery by a single surgeon. Immediate mortality, surgical complications and long term results in terms of symptoms recurrence, were analyzed. Results: The underlying diagnoses of the operated patients were Barrett's esophagus or esophagitis in 257, hiatal hernia in 91, achalasia in 68 and esophageal diverticula in five. Surgery obtained successful results in 90% of patients with Barrett's esophagus. Among patients with hiatal hernia, there was a 12% rate of complications and a 30% recurrence, when a mesh was not used. Among patients with achalasia the recurrence rate was less than 5%. Conclusions: Laparoscopic surgery has a fair success rate in benign esophageal diseases, with a lower rate of complications.

Cutaneous necrosis caused by acenocumarol. Case report Cutaneous necrosis is a rare but serious complication, among patients treated with warfarin or aceno- cumarol derivatives. We report a 71 years old female with a history of deep venous thrombosis, receiving acenocumarol for three months. The treatment was discontinued, but had to be restarted, due to a new episode of thrombosis. Three days after restarting acenocumarol, the patient consulted for ecchymosis and pain of the right foot. At physical examination, there was distal cyanosis and absence of distal pulses. The patient was subjected to an embolectomy with the suspicion of an acute arterial occlusion, but no emboli were found. Due to the possibility of a cutaneous necrosis caused by Acenocumarol, the medication is discontinued. The cutaneous lesions progressed and eight days after the failed embolectomy, a gangrene of the right foot was diagnosed. The patient did not accept amputation dying fourteen days after the fi rst intervention.

A propósito un caso registrado, se resume la historia clínica y se revisa la literatura, dada la escasa frecuencia de esta complicación derivada del tratamiento por anticoagulantes orales. La necrosis cutánea es un evento adverso raro, pero serio, de la anticoagulación con derivados de acenocumarol o warfarina. Se comunicó por primera vez en 1943. La incidencia de la necrosis cutánea inducida por anticoagulantes orales es de 0,01 al 0,1% de los pacientes tratados. El número de casos publicados en el mundo es de aproximadamente 300, y menos de 100 en lengua inglesa en las últimas tres décadas. Este trabajo reporta el caso de una paciente que presenta necrosis cutánea en hombro izquierdo y pierna derecha. Cutaneous necrosis is a rare but serious complication, among patients treated with warfarin or acenocumarol derivatives. We report a 71 years old female with a history of deep venous thrombosis, receiving acenocumarol for three months. The treatment was discontinued, but had to be restarted, due to a new episode of thrombosis. Three days after restarting acenocumarol, the patient consulted for ecchymosis and pain of the right foot. At physical examination, there was distal cyanosis and absence of distal pulses. The patient was subjected to an embolectomy with the suspicion of an acute arterial occlusion, but no emboli were found. Due to the possibility of a cutaneous necrosis caused by Acenocumarol, the medication is discontinued. The cutaneous lesions progressed and eight days after the failed embolectomy, a gangrene of the right foot was diagnosed. The patient did not accept amputation dying fourteen days after the first intervention.

Intestinal tuberculosis causing a severe gastrointestinal bleeding. Report of one case We report a 27 years old woman presenting with hematochezia. An upper endoscopy and colonoscopy did not reveal the bleeding site. Due to persistence of bleeding, the patient was operated, fi nding a fi brinous secretion surrounding bowel loops and a hyper vascularized concentric papular lesion. The involved bowel loop was excised. The pathological study of the surgical piece revealed intestinal tuberculosis. The patient started treatment for extra pulmonary tuberculosis.

Minimally invasive surgery has the advantage of a lower rate of complications and can be used for benign esophageal diseases.To report a single surgeon experience with laparoscopic surgery for benign esophageal diseases.Prospective analysis of 421 patients (160 males) with benign esophageal disease, who were subjected to laparoscopic surgery by a single surgeon. Immediate mortality, surgical complications and long term results in terms of symptoms recurrence, were analyzed.The underlying diagnoses of the operated patients were Barrett's esophagus or esophagitis in 257, hiatal hernia in 91, achalasia in 68 and esophageal diverticula in five. Surgery obtained successful results in 90% of patients with Barrett's esophagus. Among patients with hiatal hernia, there was a 12% rate of complications and a 30% recurrence, when a mesh was not used. Among patients with achalasia the recurrence rate was less than 5%.Laparoscopic surgery has a fair success rate in benign esophageal diseases, with a lower rate of complications.